Cyclohexanedimethanols are important intermediates for producing a variety of polyesters for coatings, fibers, molding plastics, packaging materials, and the like. Cyclohexanedimethanols are typically manufactured by the hydrogenation of the corresponding cyclohexanedicarboxylate esters. For example, one of the more commercially important cyclohexanedimethanols, 1,4-cyclohexanedimethanol (abbreviated herein as “CHDM”), typically is prepared by a two-step hydrogenation process involving hydrogenation of dimethyl isophthalate (abbreviated herein as “DMT”), to give dimethyl 1,4-cyclohexanedicarboxylate (abbreviated herein as “DMCD”), followed by hydrogenation of the ester groups. The various steps of this process have been described, for example, in U.S. Pat. Nos. 3,334,149, 6,919,489; 5,399,742; 5,387,752; 5,395,987; 5,185,476; and 7,632,962; and United Kingdom Patent Application No. 988,316. The preparation of 1,3-cyclohexanedimethanol (abbreviated herein as “1,3-CHDM”) can be carried out in an analogous manner by hydrogenation of dimethylisophthalate (abbreviated herein as “DMI”) to dimethyl cyclohexane-1,3-dicarboxylate that can be further hydrogenated to 1,3-CHDM.
The use of DMI as starting material for the preparation of 1,3-CHDM presents several challenges. DMT is typically prepared by the esterification of isophthalic acid with methanol under high pressures and temperatures. DMI must also be distilled prior to its introduction into the hydrogenation step of the 1,3-CHDM process in order to remove partial esterification products and any esterification catalysts that can poison and/or reduce the activity of the downstream hydrogenation catalysts. Finally, the hydrogenation of DMI releases methanol that requires additional purification and processing steps in order to recover and recycle the methanol from the 1,3-CHDM hydrogenation product mixtures. The use of alternative 1,3-CHDM feedstocks that avoid these difficulties, therefore, could greatly improve the efficiency and reduce the equipment and processing costs of the 1,3-CHDM process.